TXA.sub.2 is a substance derived from arachidonic acid in vivo and has various physiological actions such as vasoconstriction and platelet aggregation. An enhancement of TXA.sub.2 synthesis is observed in some patients with angina pectoris. Therefore, it is considered that TXA.sub.2 is implicated as a causitive material in ischaemic heart disease.
More particularly, arachidonic acid is transformed to prostaglandin G.sub.2 and prostaglandin H.sub.2 by cyclooxygenase. Prostaglandin G.sub.2 and prostaglandin H.sub.2 are transformed to prostacyclin (hereinafter abbreviated as PGI.sub.2), prostaglandin E.sub.2 (hereinafter abbreviated as PGE.sub.2), prostaglandin F.sub.2.alpha. (hereinafter abbreviated as PGF.sub.2.alpha.), TXA.sub.2 and the like by various enzymes in various tissues and organs.
As compounds inhibiting the synthesis of TXA.sub.2,a cyclooxygenase inhibitor such as acetylsalicyclic acid and indomethacine, and a TXA.sub.2 synthetase inhibitor are reported. The cyclooxygenase inhibitor suppresses not only the synthesis of TXA.sub.2 but the synthesis of other prostaglandins such as PGI.sub.2, PGE.sub.2 and the like. PGI.sub.2 has opposite physiological actions to those of TXA.sub.2, for example, a powerful vasodilation and inhibition of platelet aggregation. Accordingly, for the above diseases the inhibition of PGI.sub.2 synthesis is not preferred.
While, the TXA.sub.2 synthetase inhibitor suppresses the synthesis of TXA.sub.2 but enhances the synthesis of PGI.sub.2. Therefore, the use of the TXA.sub.2 synthetase inhibitor is preferred for the above diseases.
Recently, some compounds having the TXA.sub.2 synthetase inhibition activity have been proposed as disclosed in Japanese Patent Application (OPI) Nos. 52272/83 and 27874/84 (the term "OPI" as used herein refers to a "published unexamined Japanese Patent Application). The former describes 2-(1-imidazolylmethyl)naphthalene-6-carboxylic acid and 1-methyl-2-(3-pyridylmethyl)naphthalene-7-carboxylic acid and the latter describes 1,2,3,4-tetrahydro-2-(1-imidazolyl)naphthalene-7-carboxylic acid. However, these known compounds do not exhibit a sufficient selective inhibition of TXA.sub.2 synthesis.